Manufacture of carbon black



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PATENT- OFFICE UNITED- STATES ALFRED w. FRANCIS, or

:PETROLEUM COMPANY,

J CINT-STOCK ASSOCIATION MANUFACTURE or CARBON BLACK Application led May 4, 1927. Serial N0. 188,794..

This invention relates to manufacture of carbon black; and in particular it relates to processes of and apparatus for manufacturing carbqnblack, wherein continuouspartial combustion of carbonaceous material is effected under superatmospheric pressure and under operating Conditions enabling deposition and recovery of a carbon black of desirable characteristics.

, The invention has for one of its objects the manufacture of carbon blackby the partial combustion of natural gas or other hydrocarbons or other carbonaceous material by operating in suoli a manner as to obtain a product of good quality andrelatively high yields.

Another obj ect of the invention is the production of carbon. black in such a way that the heat of combustion of the fuel can be 'conserved and utilized in the production of power, instead of being wasted as has been the usual practice heretofore.

Other and further objects and the advantages of the invention will become apparent as the description proceeds. n

According to one method Y, heretofore known, a grade of carbon black satisfactory for lprinters ink and for rubber compounding and many other uses has been obtained upon a metal plate from a luminous flame of natural gas burning in the open air, but the yield always has been low, seldom exceeding four per cent. Attempts have been made to increase the yield by par! `tially'smotheringthe llame by means of an inert gas such as carbon dioxide or nitrogen, or by limiting the vsupply of minish the combustion of carbon, but these expedients have not accomplished their'purpose.

The reason for this will appear presently.

. The manufacture of carbon black by ther-rv mal decomposition of hydrocarbon gases,

which is 'another method already known, can-be made to'give thirty or forty per cent yields of carbon, but because of the high ltemperature required for a reasonable reaction rate, 1200o to 1300 C., the product is quite different, and entirely unfit for use in ink, being inferior in tinctorialA printers power. It ifs also less satisfactory for rubployed.

ber compounding. Moreover, the high temperature and large input of heat required make the `process costly, and since the conditions are very corrosive to equipment, the repair costs are high.

By the method of the present invention it is possible to obtain by continuous partial combustion of hydrocarbons or other carbonaccous material a much higher yield of carbon black than was obtainable by the combustion processes heretoforeV employed. Moreover, the quality of the black produced is fully as good as the product now regarded as ,standard in color, tinctorial power, for rubber compounding, and for the various other uses for which carbon black is emknown that mixtures richer than methane in air are not 1n- It is about 14 per cent flammable at ordi nary temperatures and pressures (atmospheric). Consequently, when methane is burned in air there is an inner cone of methane-rich mixture in which there is no. combustion and from which no carbon could be deposited, the boundaries of which are determined by this limiting ratio. In such a critical or limiting mixture there exists about 18 per cent oxygen, or 1.3 mols. of oxygen to one of methane, which is in excess of that called for by the ideal reaction for the maximum production of carbon:

(1) CI-LftOg--QHZO-i-C ltion corresponds more nearly with the equation (2) CIL-l- 02': CO +H2+H2O according to which there would be enough oxygen in a- 14 per cent metliane-'-86 per cent air mixture to completely gasify all of the carbon.

This is the reasonfor the low yield. The futility` of using an inert gas is thus evident,

theory and experiment agree since the flame will not extend inwards to a Zone containing an oxygen-methane ratio of less than about 1.3 regardless of the presence of inert gases. In fact when a higher percentage of inert gas is present', the limiting ratio is much higher.

In order therefore to obtain the largest yield of carbon from the partial combustion of methane, conditions should be so regu` lated as to make the reactionl taking place in the flame proceed more in accordance with equation (l) and less according to equation (2).

In accordance with the principles of the present invent-ion, this result can be obtained by burning the methane with a luminous flame under conditions of' superatmosphcric pressure; that is, by compressing separately the methane and air in a closed chamber; Moreover, the yield of carbon is approximately proportional to the working sure, the larger is theyield ofcarbon. ressures as highfas 200 pounds per square inch, gage, have given good results and even higher yields are obtainable at still higher pressures, suitable apparatus being employed to withstand such pressures. Increase in operating pressure beyond about 300 pounds, or somewhat higher, results in very sudden and disproportionate increase in yield of carbon black. Pressures above 300 pounds gage are therefore especially advantageous from the standpoint of high yield.

While the invention is not necessarily dependent upon any particular theory for suc# cessful operation in practice, but rather rests upon actually observed facts, the following considerations are suggested as possibly affording an explanation of the effectiveness lof the new process.

In the first place the results may be due in part to the fact that under pressure the upper inflammability limit of methane is increased. Iniother Words the flame extends inwards to a richer mixture of methane in air, which condition is obviously favorable to carbon production.

The second part of the explanation involves fundamental principles of gaseous equilibrium and in particular LeChateliers namel prlnciple as applied to gaseous reactions, that an increase, of pressure will cause a reaction to take place in the directioriwhicli will decrease the number of gaseous molecules in unit volume.

Since we are desirous of suppressing Equation (2), we are inpart concerned with the following reactions of carbon monoxide and hydrogen:

The equilibria represented by varrows in the above equations can be progressively shifted and burning the former pressure. Thehigher the res-` to the right by the application of increasing pressures in accordance with the principle above cited. The application of pressure will therefore be seen to favor the produ(I` tion of carbon, or conversely stated to minimize the conversion of methane to carbon monoxide and hydrogen as represented by Equation (2).

In order that the underlying principles of the invention may be still better understood, a typical way of practicing the new process to advantage will now be described in connection with the drawings which illustrates a desirable form of apparatus to employ.

In the drawings,

Fig. l is a central vertical section through i the pressure chamber, parts being shown in elevation;

Fig. 2 is a top plan view with the cover of the chamber removed; and

Fig. 3 is a side Aelevation of the scraper which' is seen in front elevation in Fig. 1.

The illustrated apparatus consists of a k"closed vessel or autoclave A, provided with a rotating disk l), driven at a slow rate by the shaft S, and the pulley I. Compressed gas, such as natural gas, for example, is Aintroduced through the burner B and tips T, and ignited by meansI of a hot wire or pilot lV, or ,other suitable means, so that the continuously burning flames impinge upon the lower surface ofthe disk D, the ignited material bcing thereby cooled below the ignition point of the liberated carbon and carbon black being deposited upon the disk. The burner tips preferably should have long thin slots such as in a laboratory flame spreader. A sight glass G, is provided for the observation of the flames. Compressed air is introduced through the inlet manifold M, below a screen F, supported by rods R, which serves to break up currents of air and prevent direct drafts upon the flames. The black deposited upon the disk D, is scraped oft' as it revolves, bby scraper K, and falls through a hopper l-l, into a compartment C1, closed by agate valre 1. At intervals V1 is opened, allowing the black to fall into lock chamberCz.4 Alter V] isvclosed, another gate valve V2 is opened, permitting the removal of theblac'k without releasing the pressure in the ,autoclave furnace A.' i

Cil

The other products of combustion, water the pressure in the furnace and yet allow the gases to escape at a rate sufficient to prevent even. partial smothering of the flames. The pressure and sensible heat of the escaping gases can be used to operate la gas engine, for the generation of power', some of which will Leaders? be required to compress fresh air for the operation. Alternatively, the heat can be. conserved by a waste heat boiler, or. by heat inter-- change used to preheat the fresh air for the than 0.8 pounds the spirit and .butane gasoline,

operation. v

'A suitable air pressure for the carrying out of the invention is `150 pounds per square inch gage. The pressure of the combustiblel gas should be at substantially the same or a slightly higher pressurel than that of the air, that is just sufficient to cause a gentie flow of gas through the burner tips; The difference in pressure between the air and gas is controlled by any suitable external dev ice, not shown, since it does not constitute a part of my invention.

In a typical instance, application of the new process to a dry natural gas from'Texas, analyzingv 88 per cent methane, 6 per cent ethanc, and 6 per cent nitrogen, gave a-yield of dry carbon black amounting to 8.12 per cent, or 2.7 pounds perv thousand cubic feet of gas burned. The gas was burned at a mean pressure of 107.5 pounds gage. Such agas would give by the ordinary partial com# bustion at va.tm'ospheric pressurenot more per thousand cubic feet.

The practice of the invention is not limited to the type of apparatus described, which is by way of illustration only. AAny other apparatus suitable for the carrying out of my process may be used Without departing from lscope ofl my invention. For lal units may be mounted ver- V example, seve "l tically above each other within the same shell,

the depositing plates or disks being driven by the same shaft and pulley, and the black being discharged by a single chute into a common compartment. Or a screw conveyor may deliver the black fromv severall autoclaves or batteries of units located beside each other into a commonlock arrangement for'removing the black.

Other fuels from which greatly increased yields have been obtained as compared to those obtained by burning them at atmospheric pressure under otherwise similar conditions are ethylene, weathering gas, Which consists essentially of propane and and paraflin Wax. All 'of these fuels where employed in the present process can be made to give higher yields than those. obtainable from methane. 'In each case the carbon black produced is satisfactory and' at least equal in'quality to high grade carbon black now onthe market.

"f Ot-ber fuels which .can be employed ad- A'vantageously by my invention are 'hydrocarbon gases such as acetylene and propylene; liquid-hydrocarbons such as gas oil, fuel oil, benzol; and even oxygenated liquids and solids ncontaining carbon such asanimal and vegetable oils and fats. In the use of liquids the burners require a slight modification, be-

V ing provided with wicks or capillary outlets,

' material under bility limit.

injected 'from a blow case ment of supcratmospheric pressures of the order of magnitude specifically mentioned hereinabove in describing a desirable way of carrying out the process. For practical puroses, however, the pressure used should be substantial and should 4ordinarily be not less than'ten pounds gage. Most desirably it should amount to several atmospheres, at least. Y

What is claimed is: l v

1 The process of partial conversion of a carbonaceous material into elementary carbon,l which comprises maintaining continuous partial combustion of said carbonaceous super-atmospheric pressure in excess of ten pounds.

2. The process of making carbon black which comprises maintaining continuous partial combustion of carbonaceous material vunder superatmospberie pressure in excess of fill ten pounds, and collecting the resultant caryl no 4. The process of making carbon blaclr which comprises maintaining continuous partial combustion of substantially wholly saturated hydrocarbon materialin an appropriate comb-ustionsupporting medium and under superatmos-pheric pressure in excess of ten pounds to increase the upper infiamma- 5. The process of fmaking carbon black which comprises maintainingi continuous partialcombustion of in an enclosed space under superatmospheric pressure in eXceslso ten pounds, collecting resultant carbon black, and utilizing the en ergy of the exhaust gases in the performance of useful Work.

' 6. The process of making carbon black which comprises maintaining continuous partial combustion of hydrocarbon material in an enclosed space under super-atmospheric pressure in excess of ten pounds, collecting resultant carbon black, and utilizing the heat and pressure of the exhaust. gases to operate aI gas engine.

7. The' process of making carbon black which comprises maintaining continuous luminous-flame lcombustion of gaseous hydrocarbon material in an enclosed space under superatmospherlc pressurev 1n excess of ten hydrocarbon material.

lll)

pounds, and collecting carbon black from the flame.

8. The process of making carbon black which comprises maintaining continuous 1nminous-flame combustion lof natural gas in anl enclosed space under superatmospherio pressure in excess of ten pounds,and collecting carbon black from the flame.

9. The process of making carbon black which comprises maintaining continuous luminous-flame combustion of gas consisting chiefly of methane in an enclosed space under Asuperatmospheric pressure in excess of ten pounds4` and collecting carbon black from the llame.

10. The process of making carboublack which comprises maintaining continuous luminous-flame combustion of gaseous substantially wholly saturated'hydrocarbon material in an enclosed space under superatmospherc pressure in excess of ten pounds, and collecting' carbon black from the lame.

ll. The process of making' carbon black which comprises maintaining continuous luminous-flame combustion of .gaseous hydrocarbon material in an enclosed space under superatmospheric pressure. amounting to sev-y eral atmospheres, and collecting carbon black from the flame.

12. The process of making' carbon black which comprises maintaining! continuous lu- Aminous-flame combustion of ,gaseous hydrocarbon material in an enclosed Vspace under.

superatmospheric pressure amountingr to at least 300 pounds, and collecting;carbon black from the flame.

13, The process oi making carbon black which' comprises maintaining' continuous partial combustion of carbonaceous material with a luminous flame in an enclosed space under superatmospheri-c pressure, the flame impinging u pon a 'suitabledepositing surface, and collectingdeposited carbon black.

14. The process set forth in,y claim 9, further characterized by the fact that the flame is shielded against excessive drafts` 15. In the process of making.: carbon black by partial'combustion of carbonaceous matvter under superatmospheric pressure 1n exwhich comprises continuously burning carbonaeeous material` With a. luminous flame surrounded by air maintained at .a pressure of at least several atmospheres, the flame impinging upon a suitable depositing surface,

and collecting deposited carbon black.

In testimony whereof'I hereunto aflx my signature. I

ALFRED W. FRANCIS. 

